Alkylamines, such as ethyleneamines, and alkanolamines, are known for their many uses in industry. Alkylamines can be broadly subcategorized into cyclic alkylamines and linear alkylamines. Piperazine (PIP) is a cyclic compound and the simplest cyclic member of the ethyleneamine family. Piperazine is used in the manufacture of plastics and resins (e.g., polyamides), other industrial materials, pesticidal compounds, and pharmaceutical compounds, such as anthelmintics With regards to alkanolamines, aminoethylethanolamine (AEEA) is an organic base with desirable chemical properties that make it a valuable intermediate for the synthesis of other compounds. The primary and secondary amine groups of AEEA, together with the hydroxyl group, combine the features of an ethyleneamine and an ethanolamine. AEEA has been used for the production of surfactants, fabric softeners, textile additives, fuel additives, chelates, and coatings.
Reductive amination of the linear alkanolamine diethanolamine (DEA) with ammonia is one way of producing PIP and AEEA. However the reductive amination of DEA can produce a variety, of non-PIP and non-AEEA products which can be of lesser economic value, and/or less useful for further processing by reductive amination. For example, U.S. Pat. No. 3,682,919 describes a process for preparing PIP and AEEA by subjecting DEA to reductive amination in the presence of a Ni—MgO (1:1) catalyst. DEA was reacted with ammonia and in the presence of the Ni—MgO catalyst at high temperatures 225° C. at a DEA conversion rate of 31 percent. Of the DEA reaction products a significant amount was non-PIP and non-AEEA products (9% monoethanolamine (MEA), 8% ethylenediamine (EDA), and 10% other amines, 27% total).
The inventors of the present application have found that these levels of non-PIP and non-AEEA products are undesirably high, and have accordingly discovered inventive methods for significantly improving the selectivity towards PIP and AEEA in the reductive amination of DEA with ammonia, while maintaining desirable reaction conditions, including moderate reaction temperatures and reactant quantities.